Specific disposable guide device for spinal surgery

ABSTRACT

Various implementations relate to a guide device for spinal surgery, comprising: two guide sleeves extending between a proximal end and a distal end for guiding a surgical intervention on a vertebra of a patient; a plurality of support elements, wherein each support element defines a contact area specifically configured for abutting against a portion of a virtual surface reproducing the vertebra of the patient, in a coupling configuration; and at least one junction element joining the two guide sleeves together. Each guide sleeve comprises a respective auxiliary sleeve extending between a proximal end and a distal end, and the proximal end of the auxiliary sleeve is located in proximity to the proximal end of the respective guide sleeve.

The present invention relates to the technical field of spinal surgery,more specifically it relates to a specific disposable guide device forspinal surgery. This device is used to help the surgeon in the drillingof a vertebra.

Vertebral drilling is often required in the field of spinal surgery, forexample for inserting a Kirschner wire, for inserting a guide wire forthe application of cannulated screws, or still for inserting solidscrews. The drilling direction must be defined with great precisionbecause the hole, which originates on the lamina, must often proceedalong a very precise direction, for example along the pedicle of thevertebra. Because of the critical nature of the drilling operation,several solutions have been developed to assist the surgeon.

First of all, techniques have been developed which, through the methodscommonly used in diagnostic imaging (for example, computerizedtomography), allow digital reconstruction of the specific anatomy of theindividual vertebra of the individual patient that must undergo surgery.

The digital model of the individual vertebra allows a physical model tobe obtained, on which the drilling is already preoperatively planned inthe finest details.

Finally, starting from the vertebra model and the drilling directiondeemed optimal by the surgeon, it is possible to construct specificdisposable guide devices for drilling. The adjective “specific” as usedherein and hereinafter means that the guide device has been customized,or shaped so as to adapt to the anatomy of a specific vertebra of aspecific patient.

In this field, guide devices are mainly employed to help the surgeonduring pedicle screw insertion, so that the screw can be insertedaccording to a pre-planned optimal axis of the screw.

However, these devices may be used in spinal surgery for other purposes;for instance, as cutting guides during PSO (pedicle subtractionosteotomies), laminotomy or facetectomies.

In general, guide devices are provided with one or more guide sleevesand one or more contact elements adapted to mate with the vertebrae ofthe patient in a stable and well-defined configuration.

Guide sleeves define the direction of advancement of the surgical tool.As the skilled person can well understand, in order to faithfullymaintain the optimal direction defined during the preoperative phase,the device must absolutely be able to be firmly rested on the vertebraand have a single well-defined position of use easily obtainable in thereal operating field.

In order to achieve this goal, a firm contact between the guide deviceand the patient's bone structure is required.

For optimal positioning of the guide, the surgeon must wash thesurrounding tissue away from a large area of the bone, and in some casescut the ligaments. This operation often proves to be difficult andcostly in terms of time and can lead to complications and lengthening ofthe patient's hospitalization.

Furthermore, the remaining tissue that the surgeon is unable to removeand the surface of the bone itself can lead to slipping and deviation ofboth the guide device and the tool used for drilling.

If this were to happen, the pedicle screws or bone resections would bepositioned incorrectly or sub-optimally.

As mentioned above, the orientation with which the surgical tool reachesthe surface of the vertebra, to perforate it, is defined by the optimaldirection the drilling must have with respect to the vertebra. For thisreason, the tool may have to reach the surface of the vertebra with astrong inclination that favours undesired displacement thereof, also dueto the slippery surface of the vertebra. In this case, therefore,despite the care taken in planning the surgical operation andconstructing the guide device, the drilling of the vertebra may besuboptimal.

In view of the foregoing, the technical problem underlying the presentinvention is to provide a disposable guide device for spinal surgery,which allows the slipping issues on the patient's vertebra to beminimized or prevented.

The aforementioned technical problem is solved by means of a guidedevice for spinal surgery, according to claim 1.

More particularly, the aforementioned technical problem is solved bymeans of a device comprising:

-   -   two guide sleeves extending between a proximal end and a distal        end for guiding a surgical intervention on a vertebra of a        patient;    -   a plurality of support elements, wherein each support element        defines a contact area specifically configured for abutting        against a portion of a virtual surface reproducing the vertebra        of the patient, in a coupling configuration; and    -   at least one junction element joining the two guide sleeves        together.

Furthermore, each guide sleeve comprises a respective auxiliary sleeveextending between a proximal end and a distal end, and the proximal endof the auxiliary sleeve is located in proximity to the proximal end ofthe respective guide sleeve.

Advantageously, each guide sleeve and the corresponding auxiliary sleevehave a diverging development starting from the respective proximal ends.

Preferably, each guide sleeve extends along a respective main axis andthe respective auxiliary sleeve extends along a respective auxiliaryaxis. Advantageously, each auxiliary axis intersects the respective mainaxis.

In accordance with some embodiments of the guide device, each auxiliaryaxis forms an angle α with the respective main axis. Preferably, theangle α formed by an auxiliary axis and the respective main axis iscomprised between 20° and 60°, even more preferably between 25° and 45°.

An insertion duct is located within each guide sleeve and a service ductis located within each auxiliary sleeve.

In some embodiments, the proximal opening of the service duct is definedin the wall of the insertion duct, near its proximal end.

In some embodiments, the proximal opening of the service duct isslightly spaced apart from the proximal opening of the insertion duct.

Both the insertion ducts and the service ducts define respectiveinsertion axes for a surgical tool whose use is preferably planned indetail in the preoperative phase.

The diameter of the insertion duct is such as to allow the insertion ofa main surgical tool. Said diameter can be selected from 3-18 mm, 3-12mm, 3-9 mm, 3-6 mm.

The diameter of the service duct is such as to allow the insertion of apreparatory drill. Said diameter can be selected from 1.8-4 mm, 2-3 mm.

Advantageously, the auxiliary axis reaches the minimum distance from themain axis in proximity to the virtual surface of the vertebra.

Preferably, the auxiliary axis intersects the main axis in proximity tothe virtual surface of the vertebra.

Preferably, the auxiliary axis reaches the minimum distance from themain axis or intersects it, at a point inside the vertebra, within 5 mmfrom the virtual surface.

Advantageously, the guide sleeves can be oriented so that the proximalends are more distant from each other with respect to the distal ends.

Preferably, each auxiliary axis forms an angle β with the portion of thevirtual surface of the vertebra on which it is incident, the angle βbeing favourable to the use of the preparatory drill.

The angle β is preferably comprised between 60° and 120°, even morepreferably between 75° and 105°.

Preferably, the at least one junction element extends transversely tothe two guide sleeves to place them in rigid connection with oneanother. More preferably, the junction element is located in proximityto the distal end of the guide sleeves.

Preferably, the guide sleeves are spaced apart from each other by adistance at least suitable to allow the housing of a spinous process ofthe vertebra to be operated on.

Preferably, the junction element takes an inverted “U” shape thatdefines therein a seat for housing the spinous process of the vertebra.

In some embodiments, the seat for housing the spinous process is open inthe craniocaudal direction.

Alternatively, the seat for housing the spinous process can be closed inthe craniocaudal direction by one or two partitions connecting the sidesof the junction element.

Preferably, the junction element comprises a handle suitable tofacilitate the surgeon's handling of the device.

Preferably, the support elements, and in particular the respectivecontact areas, are designed in a patient-specific manner during thepreoperative phase.

Preferably, at least one of the support elements is shaped like a hook,so as to at least partially encircle a portion of the vertebra.

Preferably, each guide sleeve is provided with a further own contactportion, near the proximal end, configured for abutting against aportion of the virtual surface of the vertebra.

Further features and advantages of the patient-specific disposable guidedevice according to the invention will become more apparent from thedescription, provided hereinafter, of a number of embodiments describedby way of non-limiting example with reference to the accompanyingdrawings, wherein:

FIG. 1 is a perspective view of a disposable guide device according to afirst embodiment of the invention;

FIG. 2 is a perspective view of a disposable guide device according to asecond embodiment of the invention when it is approached to therespective vertebra;

FIG. 3 shows a view similar to that of FIG. 2 in which the guide deviceis correctly resting on the respective vertebra;

FIG. 4 shows a different view of the device of FIG. 2 correctly restingon the respective vertebra;

FIG. 5 shows a cross section made along the line V-V in FIG. 4 ;

FIG. 6 is a perspective view of a disposable guide device according to athird embodiment of the invention correctly resting on the respectivevertebra;

FIG. 7 shows a different view of the device of FIG. 6 correctly restingon the respective vertebra; and

FIG. 8 shows a cross section made along the line VIII-VIII in FIG. 7 .

With reference to the accompanying figures, the numeral 10 indicates aguide device for spinal surgery according to the present invention.

In particular, the figures show the device 10 approached to a specificvertebra 100 for which it was designed and constructed.

The disposable guide device 10 for spinal surgery comprises:

-   -   two guide sleeves 12 extending between a proximal end 14 and a        distal end 16 for guiding a surgical intervention on a vertebra        100 of a patient;    -   a plurality of support elements 18, wherein each support element        18 defines a contact area 20 specifically configured for        abutting against a portion of a virtual surface 102 reproducing        the vertebra 100 of the patient, in a coupling configuration;        and    -   at least one junction element 22 joining the two guide sleeves        12 together.

In the disposable guide device 10 according to the invention, each guidesleeve 12 comprises a respective auxiliary sleeve 24 extending between aproximal end 26 and a distal end 28, and the proximal end 26 of theauxiliary sleeve 24 is located in proximity to the proximal end 14 ofthe respective guide sleeve 12.

Reference is made herein and hereinafter to a virtual surface 102reproducing the vertebra 100 of the patient. As known per se, thisvirtual surface 102 is obtained from the three-dimensional model of thepatient's vertebra 100. A specific virtual surface 102 is thereforeuniquely identified for each individual guide device 10. Moreover, whenthe guide device 10 is correctly arranged in the coupling configuration,its position is uniquely defined with respect to the virtual surface102. Due to the uniqueness of the virtual surface 102 and the uniquenessof the reciprocal position between the same and the guide device 10 inthe coupling configuration, some features of the guide device 10 can bedefined unambiguously in relation to the virtual surface 102. In thepresent discussion, the expressions “in use”, “during use” or the likerefer to the guide device 10 in the configuration of coupling to thevirtual surface 102.

Since the virtual surface 102 faithfully reproduces the vertebra 100, inthe attached figures it is represented as resting on the vertebra 100itself and can actually be identified as the real surface of thevertebra 100, without however introducing ambiguities or errors.

Advantageously, each guide sleeve 12 and the corresponding auxiliarysleeve 24 have a diverging development starting from the respectiveproximal ends 14, 26.

Preferably, each guide sleeve 12 extends along a respective main axis Xpand the respective auxiliary sleeve 24 extends along a respectiveauxiliary axis Xa. In this case, advantageously, each auxiliary axis Xaintersects the respective main axis Xp.

In accordance with some embodiments of the guide device 10, eachauxiliary axis Xa forms an angle α with the respective main axis Xp.

Preferably, the angle α formed by an auxiliary axis Xa and therespective main axis Xp is comprised between 20° and 60°, even morepreferably between 25° and 45°.

If the main axis Xp and the secondary axis intersect, they lie in thesame plane and the angle α is immediately identifiable by the skilledperson. Vice versa, if there is no plane containing both the main axisXp and the auxiliary axis Xa (i.e. in the case where these axes areskew), it is possible, for example, to consider by analogy the angleformed by the projections of the axes on a plane perpendicular to thesegment that represents the minimum distance between the two axes.

Note that the terms “distal” and “proximal”, as used herein, refer tothe relative position of an element (e.g. the end of a sleeve) withrespect to the virtual surface 102 of the vertebra 100.

Each guide sleeve 12 houses an insertion duct 30 extending withsubstantial continuity between the distal end 16 and the proximal end14. In other words, the insertion duct 30 extends between a distalopening 32, formed in the distal end 16 of the guide sleeve 12, and aproximal opening 34, formed in the proximal end 14 of the guide sleeve12.

Similarly, each auxiliary sleeve 24 houses a service duct 36 extendingwith substantial continuity between the distal end 28 and the proximalend 26. In other words, the service duct 36 extends between a distalopening 38, formed in the distal end 28 of the auxiliary sleeve 24, anda proximal opening 40, formed in the proximal end 26 of the auxiliarysleeve 24.

In accordance with some embodiments (see, for example, FIGS. 6-8 ), theproximal opening 40 of the service duct 36 is defined in the wall of theinsertion duct 30, near its proximal end 14. In these embodiments, theservice duct 36 opens into the insertion duct 30.

In other embodiments (see, for example, FIGS. 1-5 ), the proximalopening 40 of the service duct 36 is slightly spaced apart from theproximal opening 34 of the insertion duct 30.

Both the insertion ducts 30 and the service ducts 36 define respectiveinsertion axes for a tool whose use is preferably planned in detail inthe preoperative phase.

Therefore, in each duct 30, 36, the distal opening 32, 38 corresponds toan access opening of a tool, while the proximal opening 34, 40 faces thepatient's vertebra 100, in the vicinity of the same.

Tools that can be used with the guide device 10 can typically be: aKirschner wire, a cannulated polyaxial screw, a solid polyaxial screw, adrill, a tapper, a punch, a probe, a marker, a pin. These tools arereferred to hereinafter as the “main surgical tools” since it is thesethat carry out the main phase of the surgical intervention. A mainsurgical tool 42 is schematically represented in FIGS. 1, 2 and 5 .

In a known manner, therefore, the diameter of the insertion duct 30 issuch that it allows the insertion of a main surgical tool 42. Dependingon the areas of application, the inner diameter of the insertion ductscan be selected from 3-18 mm, 3-12 mm, 3-9 mm, 3-6 mm.

In accordance with the invention, the diameter of the service duct 36 issuch that it allows the insertion of a preparatory drill. Depending onthe areas of application, the inner diameter of the insertion ducts canbe selected from 1.8-4 mm, 2-3 mm. Such a preparatory drill has the taskof superficially incising the bone to facilitate the use of the mainsurgical tool 42.

In light of the above, the skilled person can readily understand thatthe main axis Xp of the guide sleeve 12 defines the direction ofadvancement of the insertion duct 30, hence of the main surgical tool42. Similarly, the auxiliary axis Xa of the auxiliary sleeve 24 definesthe direction of advancement of the service duct 36, hence of thepreparatory drill (not shown in the figures). The direction ofadvancement Xa of the preparatory drill can be advantageously definedduring the preoperative planning, most of all to optimally define theangle β at which the preparatory drill approaches the virtual surface102 of the vertebra 100. Some considerations on the angle β are givenbelow.

Advantageously, therefore, the auxiliary axis Xa reaches the minimumdistance from the main axis Xp in proximity to the virtual surface 102of the vertebra 100. Preferably, the auxiliary axis Xa intersects themain axis Xp in proximity to the virtual surface 102 of the vertebra100.

Preferably, as can be seen in the cross sections depicted in FIGS. 5 and8 , the auxiliary axis Xa reaches the minimum distance from the mainaxis Xp or intersects it, at a point inside the vertebra 100. Inaccordance with some embodiments, the auxiliary axis Xa reaches theminimum distance from the main axis Xp or intersects it within 5 mm fromthe virtual surface 102.

According to an optional aspect of the present invention, the guidesleeves 12 can be oriented so that the proximal ends 14 are more distantfrom each other with respect to the distal ends 16. In other words, themain axes Xp of the guide sleeves 12 are oriented, starting from therespective distal ends 16, away from each other. Therefore, the guidedevice 10 according to the present invention preferably has a“diverging” configuration, in which the guide sleeves 12 diverge in theproximal region. Advantageously, this simplifies the positioning of thedevice 10, thus reducing the space required for insertion by thesurgeon.

As the skilled person can well understand, the orientation of eachauxiliary sleeve 24 can be chosen rather freely during the design of thedevice 10. In particular, the orientation with respect to the virtualsurface 102 of the vertebra 100 can be defined regardless of thedirection Xp to be followed by the main surgical tool 42.

The orientation and positioning of the guide sleeves 12 and therespective auxiliary sleeves 24 are designed during the preoperativephase, by means of computer-aided design tools, on a three-dimensionalmodel of the bone structure. This model is developed from athree-dimensional image obtained, for example, by computerizedtomography and/or magnetic resonance of the patient's vertebra 100.Therefore, each sleeve 12, 24 is designed so as to uniquely define thedirection of the respective axis Xp, Xa with respect to the vertebra100.

Preferably, the device 10 is constructed so that each auxiliary axis Xa,in use, forms an angle @ with the portion of the virtual surface 102 ofthe vertebra 100 on which it is incident, the angle β being favourableto the use of the preparatory drill. The angle @ formed, in use, by eachauxiliary axis Xa with the portion of the virtual surface 102 of thevertebra 100 on which it is incident is preferably comprised between 60°and 120°, even more preferably between 75° and 105°.

As mentioned previously, a junction element 22 is provided between thetwo guide sleeves 12.

Preferably, the at least one junction element 22 extends transversely tothe two guide sleeves 12 to place them in rigid connection with oneanother. More preferably, the junction element 22 is located inproximity to the distal end 16 of the guide sleeves 12.

Therefore, such a junction element 22 is a preferably non-straightcrosspiece extending between the two guide sleeves 12 to space themapart and keep them firmly in a pre-established mutual position.

Preferably, the guide sleeves 12 are spaced apart from each other by adistance at least suitable to allow the housing of a spinous process 104of the vertebra 100 to be operated on.

In accordance with some embodiments, the junction element 22 takes aninverted “U” shape that defines therein a seat 44 for housing thespinous process 104 of the vertebra 100.

According to some embodiments, for example those shown in FIGS. 1-4 ,the seat 44 for housing the spinous process 104 is open in thecranial-caudal direction in order to prevent the patient's ligamentsfrom having to be excised before placing the guide device 10 in thecoupling configuration (open profile).

Alternatively, for example in the embodiment shown in FIGS. 6-7 , theseat 44 for housing the spinous process 104 can be closed in thecranial-caudal direction by one or more partitions 46 connecting thesides of the junction element 22, respectively forming a semi-open orclosed profile surrounding the spinous process 104, so as to ensureexcellent stability to the guide device 10.

According to a further optional aspect of the present invention, thejunction element 22 preferably comprises a handle 48 suitable tofacilitate the surgeon's handling of the device 10. For instance, thehandle 48 can extend from the junction element 22 (see, for example,figures from 2 to 4). Alternatively, the handle 48 can extend similarlyto the junction element 22, joining the two guide sleeves 12 to eachother.

In order to promote the stability of the device 10, it comprises aplurality of support elements 18 preferably arranged near the proximalend 14 of each guide sleeve 12. Each support element 18 defines acontact area 20 configured for abutting against a specific portion ofthe virtual surface 102 of the patient's vertebra 100, in a couplingconfiguration.

Preferably, this portion is one side of the spinous process 104, alamina, an articular process, or a transverse process of the patient'svertebra 100. As already mentioned for the sleeves, the support elements18, and in particular the respective contact areas 20, are also designedduring the preoperative phase, by means of computer-aided design tools,on a three-dimensional model of the bone structure. This model isdeveloped from a three-dimensional image obtained, for example, bycomputerized tomography and/or magnetic resonance of the patient'svertebra 100. Therefore, each contact area 20 of the support elements 18is designed so that it uniquely matches the bone structure of thepatient.

In some embodiments, at least one of the support elements 18 is shapedlike a hook. In other words, this support element 18 comprises a contactarea 20 which is shaped as a whole so as to at least partially encirclea portion of the vertebra 100 and to rest on the vertebra 100 fromdifferent directions. By way of example, in the embodiment in figuresfrom 2 to 4, it can be seen that the two support elements 18 are bothshaped like a hook, so that each one defines a contact area 20 designedto rest on the arch or lamina of the vertebra 100 partly in the cranialdirection and partly in the caudal direction.

Advantageously, this allows a reduced, but particularly firm supportarea to be obtained.

In certain embodiments, each guide sleeve 12 is also provided with afurther contact portion 50, also located near the proximal end 14 of theguide sleeve 12 and configured to abut against a portion of the virtualsurface 102 of the vertebra 100. Preferably, this contact portion 50,just like the contact areas 20, is also shaped complementarily to thevirtual surface of the respective portion of the patient's individualvertebra 100.

The invention achieves the intended objects and attains importantadvantages.

In fact, the presence of the auxiliary sleeves 24 allows the surgeon toincise the surface of the vertebra 100 by operating along a direction Xawhich is more favourable than that of the guide sleeves 12.

Once the preparatory drill has made the surface incision, the insertionof the main surgical tool 42 is considerably simplified and therefore isnot likely to undergo dangerous deviations.

It is clear that the specific features are described in relation todifferent embodiments of the invention for illustrative and non-limitingpurposes. Obviously, a person skilled in the art can make furthermodifications and variations to the present invention in order to meetcontingent and specific requirements. For instance, the technicalfeatures described in relation to one embodiment of the invention may beextrapolated from it and applied to other embodiments of the invention.Such modifications and variations also fall within the scope ofprotection of the invention as defined in the following claims.

The invention claimed is:
 1. A disposable guide device for spinalsurgery, comprising: two guide sleeves extending between a proximal endand a distal end for guiding a surgical intervention on a vertebra of apatient; a plurality of support elements, wherein each support elementdefines a contact area specifically configured for abutting against aportion of a virtual surface reproducing the vertebra of the patient, ina coupling configuration; at least one junction element joining the twoguide sleeves together, wherein each guide sleeve comprises a respectiveauxiliary sleeve extending between a proximal end and a distal end theproximal end of the auxiliary sleeve is located in proximity to theproximal end of the respective guide sleeve.
 2. The guide deviceaccording to claim 1, wherein each guide sleeve and the respectiveauxiliary sleeve have a diverging development starting from therespective proximal ends.
 3. The guide device according to claim 1,wherein each guide sleeve extends along a respective main axis andwherein the respective auxiliary sleeve extends along a respectiveauxiliary axis.
 4. The guide device according to claim 3, wherein eachauxiliary axis intersects the respective main axis.
 5. The guide deviceaccording to claim 3, wherein each auxiliary axis forms an angle withthe respective main axis.
 6. The guide device according to claim 5,wherein the angle is between 20° and 60°.
 7. The guide device accordingto claim 3, wherein the auxiliary axis reaches a minimum distance fromthe main axis in proximity to the virtual surface of the vertebra. 8.The guide device according to claim 3, wherein the auxiliary axisreaches a minimum distance from the main axis or intersects the mainaxis, at a point inside the vertebra, within 5 mm from the virtualsurface.
 9. The guide device according to claim 3, wherein eachauxiliary axis forms an angle with the portion of the virtual surface onwhich the auxiliary axis is incident, the angle being favourable to theuse of a preparatory drill.
 10. The guide device according to claim 9,wherein the angle is between 60° and
 120. 11. The guide device accordingto claim 1, wherein the guide sleeves are oriented so that theirproximal ends are further away from each other than the distal ends. 12.The guide device according to claim 1, wherein at least one of thesupport elements is shaped like a hook, so as to at least partiallyencircle a portion of the vertebra.
 13. The guide device according toclaim 1, further comprising a handle.
 14. The guide device according toclaim 6, wherein the angle is between 25° and 45°.
 15. The guide deviceaccording to claim 10, wherein the angle is between 75° and 105°.